The present disclosure relates to industrial process control or monitoring systems. More specifically, the present disclosure relates to paddle style orifice plates and process variable transmitters of the type which use paddle style orifice plates to measure a process variable of an industrial process.
In industrial settings, control systems are used to monitor and control inventories of industrial and chemical processes, and the like. Typically, the control system that performs these functions uses field devices distributed at key locations in the industrial process and coupled to control circuitry in the control room by a process control loop. The term “field device” refers to any device that performs a function in a distributed control or process monitoring system, including all devices used in the measurement, control and monitoring of industrial processes.
Some field devices include a transducer which couples to the process fluid. A transducer is understood to mean either a device that generates an output signal based on a physical input or that generates a physical output based on an input signal. Typically, a transducer transforms an input into an output having a different form. Types of transducers include various analytical equipment, pressure sensors, thermistors, actuators, solenoids, indicator lights, and others.
Field devices, such as process variable sensors used in industrial processes can be installed in the field on pipelines, tanks and other industrial process equipment. Such devices sense process variables such as process fluid flow, process fluid temperature, process fluid pressure, process fluid conductivity, process fluid pH and other process variables. Other types of industrial process field devices include valves, actuators, field controllers, data displays and communication equipment such as industrial field network bridges.
One type of process variable sensor is a flow meter that can measure a rate of fluid flow, for example. Measuring flow in a pipe is a standard metric many industries need. The use of paddle style orifice plates to measure differential pressure flow is one of the most popular methods in use today. One drawback for using a paddle style orifice plate is that it is only one of several components necessary to make a measurement in a pipeline. Normally, an orifice plate is installed to create a restriction in the flow. Pressure measurements are taken just upstream and downstream of the plate using pressure ports. Typically, the pressure ports are located in special connection flanges welded into the pipeline. From these flanges the separate pressures are connected to a manifold that is attached to a differential pressure transmitter. The plate, flange tap flanges, valves, impulse tubes, instrument manifolds, and a transmitter are all separate components that must be procured and connected to make the measurement.
An alternative to the use of paddle style orifice plates is wafer style integrated flow meters which can be bolted into a pipe and connected to a data control system to get a flow measurement. However, even with the evolution of orifice plates into wafer style integrated flow meters, some users of industrial process control or monitoring systems are reticent about changing their standard practices to incorporate the newer technology associated with the wafer style integrated flow meters. In spite of combining numerous components into an integrated flow meter, some of these users do not like the additional width that comes with a wafer-type meter. The exposed bolts that span the wafer between the process flanges can be perceived as a safety risk if the fluid in the pipe is hazardous. However the narrower width of a paddle style orifice plate, typically in the range of 0.125-0.25″, does not carry the same exposed bolt perception.
Testing and other complications can limit wafer style integrated flow meters in size and materials. Expensive testing is frequently required to make a new line size and new calibration values. One reason for this can be due to the flow lab testing time required to create a formula correcting the plate's performance in different pipe schedules. Materials can be difficult to source for various tubing sizes and expensive to weld test. These and other reasons can make the use of paddle style orifice plate flow meters more desirable in certain circumstances or by some users, yet the above-discussed disadvantages of paddle style orifice plates remain.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.